Such administration sets customarily include a length of plastics tubing, frequently p.v.c. and rely upon compression of this tubing by a clamp to control the rate of flow. The degree or position of compression is variable to vary the rate of flow and a problem is that "creep", i.e., cold flow of the plastics material after setting of the clamp, leads to alteration in the passage through the clamped section of tubing.
Various solutions have been proposed to this problem, as for example in United Kingdom Patent Specifications Nos. 1,319,090 (Adelberg) and 1,361,405 (Clarke).